JavaScript Object and multiple ways to create it

In JavaScript, objects are king.

What is Object?

In JavaScript, almost “everything” is an object.

• Booleans can be objects (if defined with the new keyword)
• Numbers can be objects (if defined with the new keyword)
• Strings can be objects (if defined with the new keyword)
• Dates are always objects
• Maths are always objects
• Regular expressions are always objects
• Arrays are always objects
• Functions are always objects
• Objects are always objects

All JavaScript values, except primitives, are objects.

JavaScript defines 5 types of primitive data types:

• string
• number
• boolean
• null
• undefined

Primitive values are immutable

Object Creation

1. Using the Object() constructor:

let obj = new Object();

This is the simplest way to create an empty object.

2. Using Object.create() method:

let obj = Object.create(null);

This method creates a new object extending the prototype object passed as a parameter.

3. Using the bracket’s syntactig sugar:

let obj = {};

This is equivalent to Object.create(null) method, using a null prototype as an argument.

4. Using a function constructor:

let ObjCreate = function(name) {
  this.name = name
}
let obj = new ObjCreate("abhayjain13");

What the new operator does is call a function and setting this of function to a fresh new Object, and binding the prototype of that new Object to the function's prototype. As is:

function f {};

new f(a, b, c);

Would be equivalent to: 

// Create a new instance using f's prototype.
let newInstance = Object.create(f.prototype)
let result;

// Call the function
result = f.call(newInstance, a, b, c),

// If the result is a non-null object, use it, otherwise use the new instance.
result && typeof result === 'object' ? result : newInstance

5. Using the function constructor + prototype:

function myObj(){};
myObj.prototype.name = "abhayjain13";
let obj = new myObj();

6. Using ES6 class syntax:

class myObject  {
  constructor(name) {
    this.name = name;
  }
}
let obj = new myObject("abhayjain13");

7. Singleton pattern:

let obj = new function(){
  this.name = "abhayjain13";
}